1. Field of the Invention
The present invention relates to an optical inspection system and more particularly to an optical inspection system having a threshold circuit responsive to the highest and lowest peak in an analog signal representative of information derived from an inspected item. The threshold circuit includes threshold setting means for setting a threshold in response to the highest and lowest peaks sensed. A comparator means compares the analog signal with the set threshold and converts the analog signal to a binary signal. An indicator means is provided responsive to the highest and lowest peaks in the analog signal for generating a visual indication of the difference between the highest and lowest peaks.
2. Background of the Invention
There are many known optical inspection systems in the prior art. Generally, the known systems are quite complex and process large amounts of data which reduces the speed of the system and increases the cost. The present invention overcomes some of the disadvantages associated with the prior art systems by sensing less information but insuring that the sensed information is significant. Because less information is sensed, less data processing is required and a faster, less expensive system is provided.
Additionally, prior art systems have had problems compensating for the contrast on an item to be inspected. The ambient light reflecting off an object to be inspected can vary rapidly and cause false readings in the system. The present invention overcomes this disadvantage by the utilization of a threshold circuit which automatically compensates for changes in the ambient light and by providing the user of the system with an instantaneous visual indication of the contrast present on an item to be inspected.